CN114716256B - Refractory material for smelting rare earth steel and method for improving rare earth yield - Google Patents
Refractory material for smelting rare earth steel and method for improving rare earth yield Download PDFInfo
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Abstract
The invention discloses a refractory material for smelting rare earth steel and a method for improving rare earth yield, belongs to the technical field of ferrous metallurgy, and solves the problem of low rare earth element yield in the existing rare earth steel smelting process. The refractory material for smelting rare earth steel is a magnesium refractory material and contains MgO in percentage by mass>90％，SiO 2 <3%, the balance being some impurities and volatiles, and binder. According to the invention, by improving ladle lining materials, tundish materials, stopper rod materials, long water gap materials, immersed water gap materials and water feeding gap materials, the rare earth element yield in the refining-continuous casting process is effectively improved. The refractory material and the control method thereof of the invention lead the yield to be about 50 percent in the refining-continuous casting process, which is improved by about 17 percent compared with the prior rare earth yield, and reduces the production cost by 100 yuan per ton of steel.
Description
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a refractory material for smelting rare earth steel and a method for improving rare earth yield.
Background
The action mechanism and action effect of rare earth in steel have been reported in a large number of documents, and the addition of rare earth in steel can obviously improve the structure of steel and improve the performance of steel. However, due to the special physical and chemical properties of rare earth metals, such as low density, easy volatilization, strong oxygen affinity and the like, the rare earth steel is seriously oxidized and burnt in the smelting process, and the rare earth yield is always lower. In laboratory or single furnace test, the rare earth yield is controllable, or the rare earth yield is not an essential and serious problem, but for continuously producing rare earth steel by adopting a continuous casting process, the stable addition of rare earth, the stable retention of rare earth in the steel and the like become key problems.
The rare earth yield in the rare earth steel production practice is between 21 and 39 percent, the fluctuation is large, and the rare earth components in the product are unstable. It is therefore highly desirable to provide a control method that reduces rare earth losses during the smelting of rare earth steels.
Disclosure of Invention
In view of the above analysis, the invention aims to provide a refractory material for smelting rare earth steel and a method for improving rare earth yield so as to solve the problem of low rare earth element yield in the existing rare earth steel smelting process.
The aim of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a refractory material for smelting rare earth steel, wherein the refractory material is a magnesium refractory material, and MgO is contained in percentage by mass>90％，SiO 2 <3% of impurities, volatile matters and adhesive in balance.
Further, the refractory material is ladle lining, tundish, stopper rod and long steel ladleThe water gap, the immersed water gap and the upper water gap refractory material contain 91-94.5% of MgO by mass percent and SiO 2 1% -2.5%.
On the other hand, the invention also provides a method for improving the rare earth yield, which comprises the following steps:
in the steps 1 to 3, the ladle lining, the tundish, the stopper rod, the long nozzle, the immersion nozzle and the upper nozzle are all made of the refractory material.
Further, in the step 2, the ladle top slag components in the LF furnace refining are CaO in percentage by mass: 55-65, siO 2 ：5-8，MgO：11-15，Al 2 O 3 ：15-24，FeO+MnO＜0.5，Ce 2 O 3 +La 2 O 3 ：0.1-2.9，CaO/SiO 2 ：8.0-11。
Further, the thickness of the ladle top slag is 140-200mm.
Further, rare earth is Ce and/or La, and is added in the last step of refining in the step 2.
Further, rare earth is added in a cerium-iron and/or lanthanum-iron mode.
Further, before rare earth is added, the mass percentage of dissolved oxygen (O) in molten steel is controlled below 1.5 ppm.
In the step 3, molten steel enters a continuous casting crystallizer through a tundish, the molten steel is covered by a tundish covering agent to isolate air, and the tundish covering agent is used after the ladle top slag in refining is ground to be below 200 meshes and dried.
Further, the thickness of the tundish covering agent is 200-250mm.
Compared with the prior art, the invention has the following beneficial effects:
1. the refractory material and the control method thereof of the invention lead the yield to be about 50 percent in the refining-continuous casting process, which is improved by about 17 percent compared with the prior rare earth yield, and reduces the production cost by 100 yuan per ton of steel.
2. By improving ladle lining material, tundish material, stopper rod material, long water gap material, immersed water gap material and water feeding gap material, the rare earth element yield in the refining-continuous casting process is effectively improved.
3. The ladle top slag component is optimized by starting with the design of the ladle top slag and the tundish covering agent component which are easiest to react with the rare earth after the rare earth is added, so that the minimum rare earth consumption is obtained.
4. The tundish covering agent can use refined ladle top slag to realize recycling of waste, and the production cost is reduced to the greatest extent.
5. By the technical scheme of the invention, the utilization rate of rare earth metal, namely valuable resources, is improved, and an example is provided for the production of rare earth steel.
Drawings
FIG. 1 is a graph showing the oxygenation levels of various links from refining to continuous casting of rare earth steel before improvement;
fig. 2 shows the rare earth loss of the prior rare earth steel from refining to continuous casting.
FIG. 3 shows the oxygenation levels of the various links from refining to continuous casting of the improved rare earth steel;
fig. 4 shows the rare earth loss of each link in the refining to continuous casting process of the improved rare earth steel.
Detailed Description
A refractory for smelting rare earth steel and a method for improving the yield of rare earth are described in further detail with reference to specific examples, which are for illustrative purposes only, but the present invention is not limited to these examples.
The rare earth yield is 21-39% in rare earth steel production practice, the fluctuation is large, the rare earth components in the product are unstable, the control method for reducing the rare earth loss in the process of smelting the rare earth steel is very necessary to be researched, and the factors influencing the rare earth yield are complex.
Therefore, the invention carries out deep research on rare earth loss in the process of smelting rare earth steel, and provides a refractory material for smelting rare earth steel and a method for improving rare earth yield.
The invention provides a refractory material for smelting rare earth steel, which adopts magnesium refractory material and comprises MgO according to mass percent>90％，SiO 2 <3%, the balance being some impurities and volatiles, and binder.
Further, the refractory materials are ladle lining, tundish, stopper rod, long nozzle, immersion nozzle and upper nozzle refractory materials, the magnesia refractory materials comprise 91-94.5% of MgO by mass percent and SiO 2 1% -2.5%.
It was found in the study that the refractory material is one of factors affecting the yield of rare earth. Therefore, the invention has conducted intensive studies on refractory materials used in the process of smelting rare earth steel.
Firstly, the inventor obtains the oxygenation amount of each link in the process from refining to continuous casting of rare earth steel through thermodynamic equilibrium calculation, and obtains the relation diagrams shown in fig. 1 and 2. According to analysis, the control optimization of ladle lining materials, tundish materials, stopper rod materials, long water gap materials, immersed water gap materials, water inlet materials, ladle top slag components and tundish covering agent components can obviously reduce the rare earth loss of molten steel in the continuous casting process.
Specifically, as can be seen from fig. 1, in addition to the oxygen increase by the intake air, the remaining 90% of the oxygen increase was related to the ladle lining material, the tundish material, the stopper rod material, the long nozzle material, the immersion nozzle material, the upper nozzle material, the ladle top slag component, and the tundish covering agent component, wherein the oxygen increase related to the above refractory material was 20.2%. Accordingly, as can be seen from FIG. 2, at a rare earth addition of 50ppm, the total loss of rare earth metals in the process is 33.74ppm, which is 67.5% of the rare earth addition, wherein the loss caused by sucking air is 6.13ppm, which is 18.2% of the total loss; the loss related to ladle lining material, tundish material, stopper material, long nozzle material, immersed nozzle material and water feeding nozzle material is 12.67ppm, accounting for 37.6% of the total loss; the loss associated with the ladle top slag component and the tundish covering agent component was 14.94ppm, accounting for 44.2% of the total loss.
Secondly, the inventor aims at each of the current smelting rare earth steelThe refractory component used in the step is mainly Al 2 O 3 MgO and C, which were studied, wherein Al 2 O 3 MgO reacts with rare earth elements in molten steel as follows:
[Ce]+1/2Al 2 O 3 ＝1/2Ce 2 O 3 +[Al] ΔG1＝－26.6T－112900
2/3[Ce]+MgO＝1/3Ce 2 O 3 +[Mg] ΔG2＝－12.06T+5230
[La]+1/2Al 2 O 3 ＝1/2La 2 O 3 +[Al] ΔG3＝－34.92T－111500
2/3[La]+MgO＝1/3La 2 O 3 +[Mg]Δg4= -14.83t+5697 Δg1= -161392J/mol, Δg2= -16749J/mol, Δg3= -175159J/mol, Δg4= -21338.09J/mol when the temperature of the molten steel in the ladle is 1550 ℃.
From the above analysis, it was found that when the temperature of molten steel in the ladle was about 1550 ℃, the rare earth element in the molten steel and Al in the refractory material of the ladle 2 O 3 And MgO reacts to aggravate the erosion of the steel ladle and reduce the yield of rare earth in the steel. Wherein the rare earth element is mixed with Al 2 O 3 The reaction is particularly severe, whereas the reaction with MgO is relatively weak. Through preliminary calculation, an aluminum-magnesium ladle is used, and the refractory material contains a large amount of Al 2 O 3 The rare earth reacts with molten steel in the smelting process, so that 0.0007-0.0015% of rare earth loss can be caused, and the rare earth yield is seriously affected.
In addition, carbon in the existing refractory material can be dissolved in the process of smelting rare earth steel, so that corrosion of the refractory material is accelerated, and the service life of the refractory material is reduced.
For the reasons, mgO is adopted for ladle linings, tundish, stopper rods, long water gaps, immersed water gaps and water inlets>90％，SiO 2 <3% of magnesium refractory.
The invention also provides a method for improving the rare earth yield, which comprises the following steps:
specifically, from the smelting tapping of the step 1 to the continuous casting of the step 3, the ladle lining, the tundish, the stopper rod, the long water gap, the immersion water gap and the water feeding gap are made of magnesium refractory materials, and MgO is contained according to the mass percent>90％，SiO 2 <3%, the balance being some impurities and volatiles, and binder. The magnesium refractory material preferably contains 91-94.5 mass percent MgO and SiO 2 1% -2.5%.
Specifically, in step 2, slag formation, namely ladle top slag, is required in the refining process of the LF furnace, and the mass percentages of the components are shown in table 1.
Table 1, LF furnace ladle top slag composition wt.%
| CaO | SiO 2 | MgO | Al 2 O 3 | FeO+MnO | Ce 2 O 3 +La 2 O 3 | CaO/SiO 2 |
| 56-65 | 5-8 | 11-15 | 15-24 | ＜0.5 | 0.1-2.9 | 8.0-11 |
From the above, it is known that the ladle top slag is also one of factors affecting the rare earth yield, and thus the present invention has been conducted on the following ladle top slag. Specifically, ladle top slag: alkalinity is 5.5-6.0, caO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The melting temperature of the ladle top slag is 1380-1450 ℃, thereby reducing SiO which is easy to react with rare earth 2 The content of MgO is properly increased in order to ensure the temperature of the top slag. The concentration of the rare earth oxide is increased, so that the activity of the rare earth oxide is improved, the transfer of rare earth elements in molten steel to slag is prevented, and the yield of rare earth is improved.
Wherein Ce in the slag 2 O 3 And La (La) 2 O 3 The content of (2) is related to the rare earth component in the molten steel, namely if the molten steel only contains Ce, the slag only contains Ce 2 O 3 The method comprises the steps of carrying out a first treatment on the surface of the If the molten steel contains only La, the slag contains only La 2 O 3 The method comprises the steps of carrying out a first treatment on the surface of the If the molten steel contains both Ce and La, the slag contains Ce at the same time 2 O 3 And La (La) 2 O 3 。
Because the rare earth element has strong reducibility, the rare earth element is reduced at the temperature of refined molten steel>1500 ℃ C.) can be easily matched with SiO in the slag 2 The oxidation-reduction reaction of MnO and FeO occurs, but the oxidation-reduction reaction of FeO is weak, so that the top slag alkalinity (CaO/SiO) 2 ) Increasing from below 6 to 8-11, siO 2 The amount of oxygen transfer is reduced, and the loss of rare earth is further reduced. Adding Ce into top slag 2 O 3 +La 2 O 3 Then the activity of rare earth oxide in slag is increased, and the oxidation of rare earth element in steel is inhibited, so that the yield is ensured.
Specifically, the ladle slag thickness in refining is 140-200mm.
The rare earth steel suitable for the invention is rare earth steel added with Ce and/or La, wherein the mass percentage of the rare earth Ce+La in the rare earth steel is between 0.002 and 0.05 percent, and the rare earth steel is added in a ferroalloy mode, such as cerium iron and/or lanthanum iron. In the last step of refining in the step 2, namely when the refining process is LF furnace-RH furnace, adding the rare earth metal in a vacuum chamber of the RH furnace and adding the rare earth metal in the final circulation degassing of RH vacuum, ensuring that the rare earth metal is not contacted with oxygen in air and has no slag reaction under vacuum, and being beneficial to improving the rare earth yield; when the refining process is an LF furnace, refining is added in the LF furnace.
Before adding the rare earth alloy, the mass percentage of the dissolved oxygen (O) in the molten steel is controlled below 1.5 ppm.
The purpose of controlling the dissolved oxygen O in the molten steel before adding the rare earth alloy is to reduce the oxidation of free oxygen in the molten steel to rare earth, but in view of the limit of the current smelting technology level, the oxygen content can only be controlled to be 1.0ppm at the minimum, so the actual control level of the dissolved oxygen O in the molten steel is between 1.0 and 1.5 ppm.
After refining, the ladle is operated to a continuous casting pouring platform, molten steel enters a continuous casting crystallizer through a tundish, argon is blown into the tundish before rare earth steel is cast, the atmosphere of the tundish is kept to be inert, the tundish covering agent is used for covering the molten steel to isolate air, and conventional slag protection and/or argon atmosphere protection is adopted for molten steel injection.
Specifically, in the continuous casting process of step 3, the tundish covering agent used can be reused for ladle top slag in LF refining, and the specific compositions are shown in Table 1.
The use of the ladle top slag as a tundish covering agent is also based on the reasons and purposes described above. Since the top slag agglomerates after refining, the particle size is very large, and good dispersibility is required as a tundish covering agent, grinding and sieving are required.
The tundish covering agent is refined slag, and the specific method is to grind the refined slag to below 200 meshes (< 0.075 mm), dry and use the refined slag, and control the thickness of the tundish covering agent to be 200-250mm. Through refining of refining slag, the tundish covering agent has good dispersibility on the surface of molten steel, can isolate air and reduce air suction, so that oxygen in the air is reduced from entering the molten steel, and oxidation reaction is carried out on rare earth elements.
By the method, compared with the oxygen increasing amount before improvement, the oxygen increasing amount is reduced by 25.4 percent as can be seen from the comparison of fig. 3 and fig. 1, and the rare earth loss amount is reduced by 16.9 percent from 67.48 percent to 50.58 percent as can be seen from the comparison of fig. 4 and fig. 2. Specifically, the loss caused by ladle lining, tundish, stopper rod, long nozzle, water inlet and water inlet refractory material is reduced by 8.34%, the loss caused by ladle top slag is reduced by 3.92%, the loss caused by tundish covering agent is reduced by 2.3%, and the loss caused by air suction is reduced by 2.34%. The rare earth yield in the steel is improved from 32.52 percent to 49.42 percent in the process from refining to continuous casting, which is improved by about 17 percent, and the production cost is reduced by 100 yuan per ton of steel.
Comparative example
The 5-furnace wear-resistant steel NM400 is produced, and the production process comprises converter, LF furnace, RH furnace and continuous casting. The target components are as follows: c0.19-0.21%; si 0.55-0.65%; mn 1.45-1.60%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; cr 0.35-0.45%; ti 0.01-0.02%; ce 0.02%.
Before adding cerium-iron alloy in RH furnace refining, the average mass percentage of dissolved oxygen (O) in molten steel is 1.43ppm.
After RH is out of station, the average component content in 5 furnaces of molten steel is as follows: c0.19%; si 0.62%; mn 1.50%; p0.013%; s0.004%; cr 0.41%; ti 0.016; ce 0.0492%.
The alkalinity of ladle top slag is 5.5-6.0, caO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity:3.96, ash content 25% and volatile content 5%.
The prior ladle lining, the tundish, the stopper rod, the long nozzle, the immersion nozzle and the upper nozzle are shown in table 2.
TABLE 2 refractory composition wt/wt% for each step of smelting rare earth steel at present
| Name of the name | Al 2 O 3 | MgO | C |
| Steel ladle lining refractory material | 93.85 | 4.56 | |
| Tundish refractory material | 88.2 | 13.14 | |
| Long nozzle refractory material | 44.05 | 30.05 | |
| Slag line with long water gap | 64.73 | 25.16 | |
| Stopper rod resistant material | 71.85 | 20.16 | |
| Refractory material for water inlet | 71.83 | 20.01 | |
| Refractory material for water immersion nozzle | 57.59 |
The refractory used in each process comprises the main components, and the balance of impurities, volatile matters and adhesive.
The average composition of the molten steel in 5 furnaces in the continuous casting crystallizer is as follows: c0.19%; si 0.60%; mn 1.52%; p0.014%; s0.002%; cr 0.38%; 0.015% of Ti and 0.016% of Ce. The loss of rare earth is 0.0332 percent. The loss amount is 67.48% of the rare earth content after the RH furnace is out of the station.
Example 1
The produced steel is wear-resistant steel NM400, and the production flow is converter, LF furnace, RH furnace and continuous casting. The target components are as follows: c0.19-0.21%; si 0.55-0.65%; mn 1.45-1.60%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; cr 0.35-0.45%; ti 0.01-0.02%; ce 0.02%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is91％，SiO 2 2.5%, the balance being some impurities and volatiles, and binder.
Before adding cerium-iron alloy in RH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.45ppm.
After RH is out of the station, the chemical components of the molten steel are as follows: c0.19%; si 0.58%; mn 1.51%; p0.014%; s0.003%; cr 0.38%; ti 0.016; ce 0.0404%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.19%; si 0.60%; mn 1.52%; p0.014%; s0.002%; cr 0.38%; 0.015% of Ti and 0.0165% of Ce. The loss of rare earth is 0.0239 percent. The loss amount accounts for 59.14% of the rare earth content of the RH furnace after the RH furnace is out of the station, and is reduced by 8.34% compared with the comparative example.
Example 2
The produced steel is wear-resistant steel NM400, and the production flow is converter, LF furnace, RH furnace and continuous casting. The target components are as follows: c0.19-0.21%; si 0.55-0.65%; mn 1.45-1.60%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; cr 0.35-0.45%; ti 0.01-0.02%; ce 0.02%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 94.5 percent, siO 2 1% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in RH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.45ppm.
After RH is out of the station, the chemical components of the molten steel are as follows: c0.19%; si 0.58%; mn 1.51%; p0.014%; s0.003%; cr 0.38%; ti 0.016; ce 0.0399%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.19%; si 0.60%; mn 1.52%; p0.014%; s0.002%; cr 0.38%; 0.015% of Ti and 0.0165% of Ce. The loss of rare earth is 0.0234 percent. The loss amount accounts for 58.6% of the rare earth content after the RH furnace is out of the station, and is reduced by 8.9% compared with the comparative example.
Example 3
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; la+ce 0.0298%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 93.5 percent, siO 2 2% of impurities and volatiles, the balance being binder.
Before cerium-iron and lanthanum-iron alloy are added in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.35ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; ce 0.0370%; la 0.0381%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%;SiO 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; ce 0.0162; la 0.0148%. The loss of rare earth is 0.0441 percent. The loss amount accounts for 58.7% of the rare earth content of the LF furnace after the LF furnace is out of the station, and is reduced by 8.8% compared with the comparative example.
Example 4
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; la 0.02%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 93 percent, siO is 2 1.5%, the balance being some impurities and volatiles, and binder.
In LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.41ppm before lanthanum-iron alloy is added.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; la 0.0483%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
Tundish covering agent and pairThe proportion is the same, and the components are as follows: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; la 0.0201%. The loss of rare earth is 0.0282 percent. The loss amount accounts for 58.4% of the rare earth content of the LF furnace after the LF furnace is out of the station, and is reduced by 9.1% compared with the comparative example.
Example 5
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.03%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 92.5 percent, siO 2 1% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.34ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; ce 0.0757%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; ce 0.0311%. The loss of rare earth is 0.0446 percent. The loss amount accounts for 58.9% of the rare earth content of the LF furnace after the LF furnace is out of the station, and is reduced by 8.6% compared with the comparative example.
Example 6
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.03%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 92 percent, siO is 2 2% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.34ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; ce 0.0755%.
The ladle top slag is the same as the comparative example, the slag alkalinity is 5.5-6.0, and CaO is 55-60%; siO (SiO) 2 10-12％；Al 2 O 3 28-30％；MgO 6-8％；FeO 0.8-1.0％；MnO 0.8-1.0％；TiO 2 0.5-0.8%; the slag thickness is 138mm; the slag melting point was 1400 ℃.
The tundish covering agent is the same as the comparative example, and comprises the following components: 26.91 percent of CaO; siO (SiO) 2 6.79％；Al 2 O 3 18.35％；MgO 16.91％；Fe 2 O 3 0.57％；C 0.01％；H 2 O0.33%; alkalinity: 3.96, ash content 25% and volatile content 5%.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; ce 0.0311%. The loss of rare earth is 0.0444%. The loss amount accounts for 58.8% of the rare earth content of the LF furnace after the LF furnace is out of the station, and is reduced by 8.7% compared with the comparative example.
Example 7
The produced steel is wear-resistant steel NM400, and the production flow is converter, LF furnace, RH furnace and continuous casting. The target components are as follows: c0.19-0.21%; si 0.55-0.65%; mn 1.45-1.60%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; cr 0.35-0.45%; ti 0.01-0.02%; ce 0.02%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 92.5 percent, siO 2 1% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in RH refining furnace, the mass percentage of dissolved oxygen (O) in molten steel is 1.41ppm.
After RH is out of the station, the chemical components of the molten steel are as follows: c0.19%; si 0.58%; mn 1.51%; p0.014%; s0.003%; cr 0.38%; ti 0.016; ce 0.0323%.
Controlling the alkalinity of ladle top slag furnace slag to be 11 and CaO to be 56%; siO (SiO) 2 5.1％；Ce 2 O 3 2.5％；Al 2 O 3 22%; mgO is 14%; feO+MnO is 0.3%; the slag thickness is 180mm; the slag melting point was 1450 ℃.
The tundish covering agent is ladle top slag in RH furnace refining, and the concrete method is that the RH refining slag is ground to below 200 meshes (< 0.075 mm), and is used after drying, and the thickness of the tundish covering agent is controlled to be 200mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.19%; si 0.55%; mn 1.52%; p0.014%; s0.002%; cr 0.38%; 0.015% of Ti and 0.0160% of Ce. The loss of rare earth is 0.0163 percent. The loss amount is 50.5% of the rare earth content after the RH furnace is out of the station, and is reduced by 17% compared with the comparative example.
Example 8
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.03%.
LadleThe packing, the tundish, the stopper rod, the long nozzle, the water inlet and the water inlet are made of magnesia refractory materials, wherein MgO is 92.5 percent, siO 2 1.5%, the balance being some impurities and volatiles, and binder.
Before adding cerium-iron alloy in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.34ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; ce 0.0628%.
Controlling the alkalinity of ladle top slag furnace slag to be 8 and CaO to be 56%; siO (SiO) 2 7％；Ce 2 O 3 1.0％；Al 2 O 3 22%; mgO is 13%; feO+MnO is 0.4%; the slag thickness is 150mm; the slag melting point was 1477 ℃.
The tundish covering agent uses LF furnace refining slag, and the specific method is to grind the LF refining slag to below 200 meshes (< 0.075 mm), dry and use the LF refining slag, and control the thickness of the tundish covering agent to be 220mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; ce 0.0311%. The loss of rare earth is 0.0317%. The loss amount is 50.5% of the rare earth content after the LF furnace is out of the station, and is reduced by 17% compared with the comparative example.
Example 9
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; la 0.02%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 94.5 percent, siO 2 1% of impurities and volatiles, the balance being binder.
In LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.41ppm before lanthanum-iron alloy is added.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; la 0.0400%.
Controlling the alkalinity of ladle top slag furnace slag to be 11 and CaO to be 56%; siO (SiO) 2 5.1％；La 2 O 3 1.0％；Al 2 O 3 24%; mgO is 13%; feO+MnO is 0.4%; the thickness of the slag is 170mm; the slag melting point was 1445 ℃.
The ladle covering agent uses LF furnace refining slag, and the specific method is to grind the LF refining slag to below 200 meshes (< 0.075 mm), dry and use the ladle covering agent, and control the thickness of the ladle covering agent to be 230mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; la 0.0201%. The loss of rare earth is 0.0199%. The loss amount accounts for 49.7% of the rare earth content of the LF furnace after the LF furnace is out of the station, and is reduced by 17.8% compared with the comparative example.
Example 10
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; la+ce 0.0298%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 93 percent, siO is 2 2.5%, the balance being some impurities and volatiles, and binder.
Before cerium-iron and lanthanum-iron alloy are added in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.35ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.047%; si 0.08%; mn 1.34%; p0.009%; s0.001%; cr 0.73%; cu 0.42%; ni 0.31%; ce 0.0320%; la 0.030%.
Controlling the alkalinity of ladle top slag furnace slag to be 11 and CaO to be 65%; siO (SiO) 2 5.9％；Ce 2 O 3 +La 2 O 3 1.0％；Al 2 O 3 16%; mgO is12%; feO+MnO is 0.1%; the slag thickness is 190mm; the slag melting point was 1445 ℃.
The ladle covering agent uses LF furnace refining slag, and the specific method is to grind the LF refining slag to below 200 meshes (< 0.075 mm), dry and use the ladle covering agent, and control the thickness of the ladle covering agent to be 240mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.047%; si 0.08%; mn 1.32%; p0.009%; s0.001%; cr 0.72%; cu 0.42%; ni 0.30%; ce 0.0162; la 0.0148%. The loss of rare earth is 0.031%. The loss amount is 50% of the rare earth content after the LF furnace is out of the station, and is reduced by 17.5% compared with the comparative example.
Example 11
The produced steel is wear-resistant steel NM400, and the production flow is converter, LF furnace, RH furnace and continuous casting. The target components are as follows: c0.19-0.21%; si 0.55-0.65%; mn 1.45-1.60%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; cr 0.35-0.45%; ti 0.01-0.02%; ce 0.04%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 91 percent, siO 2 1% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in RH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.23ppm.
After RH is out of the station, the chemical components of the molten steel are as follows: c0.19%; si 0.62%; mn 1.50%; p0.013%; s0.004%; cr 0.41%; ti 0.016; ce 0.0793%.
Controlling the alkalinity of ladle top slag furnace slag to be 10 and CaO to be 60%; siO (SiO) 2 6％；Ce 2 O 3 2％；Al 2 O 3 19%; mgo=12%; feo+mno=0.4%; the slag thickness is 150mm; the slag melting point was 1434 ℃.
The ladle top slag in refining, which is used by an RH furnace, is used as a tundish covering agent, and the concrete method is that the RH refining slag is ground to below 200 meshes (less than 0.075 mm), and is used after being dried, and the thickness of the tundish covering agent is controlled to be 220mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.20%; si 0.58%; mn 1.51%; p0.013%; s0.002%; cr 0.41%; ti 0.016; ce 0.0394%. The loss of rare earth is 0.0395%, the loss of rare earth accounts for 50.3% of the rare earth content of the RH furnace after the RH furnace is out of the furnace, and the loss is reduced by 17.2% compared with the comparative example.
Example 12
The produced steel is corrosion resistant steel Q450NRQ1, and the production flow is converter-LF furnace-continuous casting. The target components are as follows: c is less than or equal to 0.12 percent; si is less than or equal to 0.75 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.025%; s is less than or equal to 0.008 percent; cr 0.30-1.25%; cu 0.20-0.55%; ni 0.12-0.65%; ce 0.008%.
The ladle lining, the tundish, the stopper rod, the long nozzle, the water immersion nozzle and the water feeding nozzle are made of magnesia refractory materials, wherein MgO is 91 percent, siO 2 1% of impurities and volatiles, the balance being binder.
Before adding cerium-iron alloy in LH furnace refining, the mass percentage of dissolved oxygen (O) in molten steel is 1.47ppm.
After LF goes out, the chemical components of molten steel are as follows: c0.048%; si 0.08%; mn 1.31%; p0.01%; s0.004%; cr 0.39%; cu 0.33%; ni 0.036%; ce 0.0167%.
Controlling the alkalinity of ladle top slag furnace slag to be 9, caO 63% and SiO 2 7％，Ce 2 O 3 1.0％，Al 2 O 3 17%, mgO=11.5%, feO+MnO=0.35%, slag thickness 150mm, slag melting point 1458 ℃.
The tundish covering agent is refined slag used by an LF furnace, and the specific method is to grind the LF refined slag to below 200 meshes (< 0.075 mm), dry the LF refined slag and then use the LF refined slag, and control the thickness of the tundish covering agent to be 220mm.
The molten steel in the continuous casting crystallizer comprises the following components: c0.048%; si 0.08%; mn 1.31%; p0.01%; s0.004%; cr 0.39%; cu 0.33%; ni 0.36%; ce 0.0083%. The loss of rare earth is 0.0084%. The loss amount is 50.4% of the rare earth content after the LF furnace is out of the station, and is reduced by 17.1% compared with the comparative example.
From the above embodiment, it can be seen that the yield of rare earth is improved by about 9% after the ladle lining, the tundish, the stopper rod, the long nozzle, the immersion nozzle and the upper nozzle are made of magnesium refractory materials. In addition, the improvement of the alkalinity of the ladle top slag is beneficial to the improvement of the rare earth yield, the rare earth loss is reduced after the ladle top slag is used as the tundish covering agent, and the oxidation caused by sucking air is correspondingly reduced. In general, the improvement of the three materials has obvious effect of improving the rare earth yield, so that the rare earth yield is stabilized at about 50%.
Claims (6)
1. A refractory material for smelting rare earth steel is characterized in that the refractory material is a magnesium refractory material, and MgO is more than or equal to 92.5% and SiO is contained in percentage by mass 2 <3%, the balance being impurities, volatile matters and adhesive; the rare earth steel is rare earth steel added with Ce and/or La, and the mass percentage of rare earth Ce+La in the rare earth steel is between 0.002 and 0.05 percent;
a method for smelting the rare earth steel by using the refractory material and improving the rare earth yield comprises the following steps:
step 1, smelting in a converter or an electric furnace;
step 2, refining in an LF furnace or an LF furnace-RH furnace;
step 3, refining and then continuously casting;
in the steps 1 to 3, the ladle lining, the tundish, the stopper rod, the long water gap, the immersion water gap and the upper water gap are all made of the refractory material;
in the step 2, the ladle top slag components in the LF furnace refining are CaO in percentage by mass: 55-65, siO 2 ：5-8，MgO：11-15，Al 2 O 3 ：15-24，FeO+MnO＜0.5，Ce 2 O 3 +La 2 O 3 ：0.1-2.9，CaO/SiO 2 :8.0-11; adding rare earth in the final step of refining in the step 2, and controlling the mass percentage of dissolved oxygen in molten steel to be below 1.5ppm before adding the rare earth;
in the step 3, molten steel enters a continuous casting crystallizer through a tundish, the molten steel is covered by a tundish covering agent to isolate air, and the tundish covering agent is used after the ladle top slag in refining is ground to be below 200 meshes and dried.
2. The refractory according to claim 1, which comprisesIs characterized in that the refractory materials are ladle linings, tundish, stopper rods, long water gaps, immersion water gaps and water feeding gaps, and MgO accounts for 92.5-94.5% by mass and SiO accounts for 2 1% -2.5%.
3. A method for improving rare earth yield by smelting rare earth steel with a refractory material according to claim 1, comprising the steps of:
step 1, smelting in a converter or an electric furnace;
step 2, refining in an LF furnace or an LF furnace-RH furnace;
step 3, refining and then continuously casting;
in the steps 1 to 3, the refractory material of claim 1 is adopted for ladle linings, tundish, stopper rods, long water gaps, immersion water gaps and water inlets;
in the step 2, the ladle top slag components in the LF furnace refining are CaO in percentage by mass: 55-65, siO 2 ：5-7，MgO：11-13，Al 2 O 3 ：17-24，FeO+MnO＜0.5，Ce 2 O 3 +La 2 O 3 ：0.1-2.9，CaO/SiO 2 :8.0-11; adding rare earth in the final step of refining in the step 2, and controlling the mass percentage of dissolved oxygen in molten steel to be below 1.5ppm before adding the rare earth;
in the step 3, molten steel enters a continuous casting crystallizer through a tundish, the molten steel is covered by a tundish covering agent to isolate air, and the tundish covering agent is used after the ladle top slag in refining is ground to be below 200 meshes and dried.
4. A method according to claim 3, wherein the ladle top slag thickness is 140-200mm.
5. A method according to claim 3, wherein the rare earth is added as cerium iron and/or lanthanum iron.
6. A method according to claim 3, wherein the tundish covering agent has a thickness of 200-250mm.
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